In prior art technology, there are many examples of cylinder lock and key combinations of the kind referred to above, having telescopic tumbler assemblies with outer pins and inner pins. In one example, disclosed in WO98/5838 (Mul-T-Lock), each tumbler assembly comprises a principle pin and a plurality of peripheral pins arranged to fit in the principle pin in a selectable non-coaxial arrangement therewith. Such a combination is quite complex, with at least three pins in each tumbler assembly, and a corresponding number of auxiliary components, such as springs and corresponding pins in the lock surrounding the rotatable key plug (denoted tumbler in this document).
Another example is an embodiment disclosed in GB 2453626 A (ASSA ABLOY Ltd.), where each telescopic tumbler pin assembly comprises an outer pin in which an inner pin is slidably mounted. The key contacting end portion of the outer pin is formed as a sleeve with a cylindrical shape having a uniform end surface. This end surface is frustro-conical, so as to provide a sliding engagement with a correctly cut key blade. The inner pin, on the other hand, has a rounded or pointed end portion, the axial position of which provides a key code. For each tumbler assembly, the code on the key blade is constituted by the axial positions of an annular seating surface (engaging with the cylindrical end portion of the outer pin) and a central dome-like projection (providing a coded seat for the end portion of the inner pin).